This invention relates a method of making pairs of cooled thread split inserts used to injection mold bottle preforms.
As seen in the applicant's U.S. Pat. No. 5,599,567 which issued Feb. 4, 1997, it is well known to use a pair of thread split inserts in a mold to form the threaded neck portion of a PET bottled preform. The neck portion of the preform also has a ring collar which is used to eject the preform from the mold. The thread split inserts have conduits through which cooling fluid is circulated to cool the neck portion of the preform prior to ejection.
In the past, thread split inserts have been made by machining steel upper and lower parts and then integrally brazing them together. This method has the disadvantage that both parts must be machined to provide cooling fluid conduits and threads and this is time consuming and therefore relatively costly.